I have an application which deals with geographical data and, in particular, tracks. Given an area (radius around geopoint, or bounding box of geopoints) I need to find, among of all these tracks, the ones that have points that interesect with said area.

For the tracks, it seems I will be dealing both with EPSG:3857 and EPSG:4326: they are either inputted by map interaction (openstreetmap, which uses EGPS:4326 data but EGPS:3857 for tiles) or GPS data (which is EGPS:4326). As for the area, I have "blank slate", but I think it will come in both forms (user either indicates an area on the map or provides an address and radius. address would be resolved with the android geocoder, which I am assuming uses EGPS:4326.)

How do I go about doing this?